Exercise Apparatus and Methods for Use

ABSTRACT

A plyometric exercise device having an elongated shaft, a hand-grip attached to the shaft, and counterweights at the two opposing ends of the elongated shaft, for use in strength development of a user&#39;s shoulder and shoulder muscles is described. Also described are methods of using such a plyometric exercise device. In use, the user typically grasps the device and moves their arm up and down, while the exercise device oscillates in phase with the user&#39;s movements in an omni-directional manner. This omni-directional movement provides both eccentric and concentric muscle contraction in the shoulder of the user, and may act to strengthen the shoulder.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims benefit of and priority to U.S. Provisional Patent Application Ser. No. 60/748,519, filed Dec. 8, 2005, the contents of all of which are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure relates to exercise apparatus and their methods of use and, more specifically, to plyometric, hand-held exercise apparatus and their use in exercising and developing upper arm and shoulder strength.

2. Description of the Related Art

Over the years, numerous exercise apparatus and machines have been developed and used by which a person can grasp by their hand and lift, for the purpose of exercising particular arm, shoulder, or back muscles of the body, both for strengthening as well as re-conditioning reasons. Due to the increasing numbers of sports which draw upon and put unnatural strain upon the complex system of muscles that form the shoulder joint and rotator cuff, attention has become more focused on exercises that are directed specifically to strengthening the shoulder musculature. The goal of such exercises and their associated exercise assemblies or apparatus is often to better stabilize and/or strengthen the head of the humerus within the Glenoid cavity, especially during times of increased external loading, as experienced, for example, during the throwing motion by a baseball pitcher, or other similar activities.

A number of exercise devices have been previously constructed to aid in the strengthening of the muscles that form the shoulder and the rotator cuff For example, a simple, isokinetic exercise device and methods for its use have been described by Hymanson in U.S. Pat. Nos. 4,964,633 and 5,147,262, respectively. These patents describe an exercise device comprising a flat, elongated metal strip having gripping handles attached to the middle portion, wherein the strip is flexible and adapted to oscillate back and forth in a bi-planar manner in response to being grasped and shaken by a user. According to the method of using this apparatus, the flexible, elongated metal strip is moved back and forth in such a way that the oscillating movements are coplanar (bidirectional), and at a rate from 3 to 7 cycles per second.

A different type of exercise device has been suggested by Yalch in U.S. Pat. No. 6,217,495 B1, describing a symmetrical swing-exercise bar having a high radius of gyration for a given total weight with the center of percussion in the distal hand grip when the exercise bar is rotated like a golf club using a two-hand grip. The swing-exercise bar reportedly has a high flexural modulus strength middle shaft section (at least 500 Kpsi) for optimum resistance in upper torso exercises, and has two weights attached to the middle section covered by hand-grips adapted for holding with two hands and adapted for use over the shoulders and neck. The device is described to be used in several different manners for exercising the body, such as by placing it across the shoulders while the user twists at the waist or flexes the shaft by the handgrips.

Yet another approach is taken in a recent exercise device describing a flexible, tubular stretching device for exercising a person's upper torso and arm muscles. This device is described to consist of a main body having a linear configuration extending substantially the length of the device, wherein the main body comprises a multi-ply electrically insulated composite of continuous plastic fiber reinforcements in an epoxy resin matrix, including alternating longitudinal and circumferential filament layers, reportedly for maintaining high tensile and compressive flexural strength. The stretching device also consists of a pair of flexible handgrips affixed at opposite ends of the device, a cushion affixed to a medial segment of the device, and an adhesive injected into the cushion for retaining the placement of said cushion on the device.

A further interesting exercise device for use in the fitness, wellness, leisure sports and aerobics fields is a wellness apparatus consisting of an elastic material in which a number of vibrations can be stimulated. The apparatus being essentially a rod or bar-shaped object. Weights can reportedly be added to the ends of the object in order to allow different exercises to be performed.

This application for patent discloses plyometric exercise apparatus' and methods for their use in fitness and wellness endeavors, including the strengthening and/or rehabilitation of the upper arm and shoulder regions of the user.

BRIEF SUMMARY OF THE INVENTION

Accordingly, in one embodiment of the present invention, a plyometric exercise apparatus is disclosed, the apparatus comprising a longitudinally extending shaft having a proximal end, a distal end, and a diameter d₂; a first counterweight and a second counterweight, having a diameter d₁, wherein the first counterweight is attached to the proximal end of the shaft and the second counterweight is attached to the distal end of the shaft; and a handle attached to the shaft intermediate between the proximal end and the distal end, wherein during operation the device has a biased, omni-directional movement, such as with a rate of oscillation ranging from about 1 to about 2.7 oscillations per second. Such an exercise apparatus preferably has a shaft, first counterweight and second counterweight comprised of a polymeric material selected from the group consisting of acetal co-polymers, acetal homo-polymers, nylon, polypropylene, and mixtures thereof

In further non-limiting aspects of this embodiment, the plyometric exercise apparatus has a ratio of counterweight diameter d₁ to shaft diameter d₂ of about 2:1, an overall length ranging from about 120 cm to about 180 cm, and is generally an elongated cylindrical shaft that is symmetrical about the longitudinal axis.

In another embodiment of the present invention, a method of exercising using a plyometric exercise apparatus which oscillates in a biased omni-directional manner during use is described, wherein the method comprises the steps of providing a plyometric exercise apparatus having an elongated shaft with counterweights at opposing ends and a substantially circular cross section which for example oscillates in the range from about 1 to about 2.7 oscillations per second; grasping the plyometric exercise apparatus near the middle of the elongated shaft; and moving the plyometric exercise apparatus back and forth at a rate so as to cause the counterweights at the opposing ends to oscillate in the omni-directional manner at a rate of oscillation. In accordance with this aspect of the invention, the back and forth movement of the user and the omni-directional oscillation of the plyometric exercise apparatus are typically not coplanar.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following figures form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these figures in combination with the detailed description of specific embodiments presented herein.

FIG. 1 illustrates a perspective view of an apparatus of the presence invention.

FIG. 2 illustrates an enlarged, cutaway view of one end of the apparatus.

FIGS. 3A-3D illustrates optional cross-sectional geometries of the shaft and/or counterweights of an apparatus of the present invention.

FIG. 4 illustrates a perspective view showing a manner in which a plyometric apparatus of the invention can be used.

FIG. 5 illustrates a side view of an alternative exercise routine for a plyometric apparatus of the present invention.

While the inventions disclosed herein are susceptible to various modifications and alternative forms, only a few specific embodiments have been shown by way of example in the drawings and are described in detail below. The figures and detailed descriptions of these specific embodiments are not intended to limit the breadth or scope of the inventive concepts or the appended claims in any manner. Rather, the figures and detailed written descriptions are provided to illustrate the inventive concepts to a person of ordinary skill in the art and to enable such person to make and use the inventive concepts.

DETAILED DESCRIPTION

One or more illustrative embodiments incorporating the invention disclosed herein are presented below. Not all features of an actual implementation are described or shown in this application for the sake of clarity. It is understood that in the development of an actual embodiment incorporating the present invention, numerous implementation-specific decisions must be made to achieve the developer's goals, such as compliance with system-related, business-related, government-related and other constraints, which vary by implementation and from time to time. While a developer's efforts might be complex and time-consuming, such efforts would be, nevertheless, a routine undertaking for those of ordinary skill the art having benefit of this disclosure.

In general terms, Applicant has created an exercise apparatus for use in exercise, for warming up before participation in a sport which the shoulders, play an integral role, or for use in strength development procedures associated with therapy of the upper arm and shoulders, including the tendons and ligaments of the upper arms and shoulders. This plyometric exercise device apparatus generally comprises a longitudinally extending shaft having a proximal end, a distal end, and an external diameter d₂; a first counterweight attached to the proximal end of the shaft and a second counterweight attached to the distal end of the shaft, the counterweights having a diameter d₁; and a handle attached to the shaft along the length of the shaft extending between the proximal end and the distal end. In accordance with aspects described herein, during typical user operation in the course of an exercise or muscle-strengthening routine, the device has a biased omni-directional movement. In certain aspects of the invention, the rate of oscillation of the exercise apparatus is from about 1 to about 2.7 oscillations per second.

As will be described in more detail herein, the shaft, the first counterweight and the second counterweight may be comprised of a variety of materials, including but not limited to polymeric materials selected from the group consisting of acetal co-polymers, acetal homo-polymers, nylon, polypropylene, and mixtures thereof Further, the diameter of the counterweights, d₁, is typically greater than the diameter of the shaft, d₂, such that the ratio of counterweight diameter d₁ to shaft diameter d₂ is about 2:1.

For the purpose of the present invention, the term “plyometric” refers to an exercise in which an eccentric muscle contraction is quickly followed by a concentric muscle contraction. In other words, when a muscle is rapidly contracted and lengthened, and then immediately followed with a further contraction and shortening, this is a plyometric exercise. This process of contract-lengthen, contract-shorten is often referred to as the “stretch—shortening cycle.” In association with this definition, an eccentric muscle contraction occurs when a muscle contracts and lengthens at the same time. An example of an eccentric muscle contraction is lowering oneself from a chin-up position. The bicep (upper arm) muscle contracts and lengthens as a person lowers themselves from the chin-up bar. A concentric muscle contraction occurs when a muscle contracts and shortens at the same time. An example of a concentric muscle contraction is lifting oneself into a chin-up position. The bicep muscle contracts and shortens as a person raises oneself up to the chin-up bar. An isometric muscle contraction occurs when a muscle contracts, but does not change in length. An example of an isometric muscle contraction is hanging from a chin-up bar with arms bent at 90 degrees. The bicep muscle contracts, but does not change in length because there is no movement up or down.

Referring now to the figures, FIG. 1 illustrates a plyometric exercise device 10 in accordance with an aspect of the present invention, comprised of a shaft 12 having a distal end 14 and a proximal end 16, counterweights 18 and 20, and handle 22. In at least one embodiment, shaft 12 as shown in FIG. 1 can be a cylindrical solid shaft that is substantially symmetrical in proportion about its longitudinal axis 15. Counterweights 18 and 20 are located at the distal and proximal ends of shaft 12, as shown, and can be formed of a solid material equivalent to that which shaft 12 is formed from. Handle 22 is located intermediate between counterweights 18 and 20 on shaft 12, and may be fixedly attached to shaft 12 (for instance, through the use of an adhesive), or may be freely movable along the length of shaft 12. In accordance with one aspect of the present disclosure, handle 22 may be fixedly attached to the approximate center of shaft 12. In accordance with further aspects of the present disclosure, handle 22 may substantially circumscribe a portion of shaft 12. Alternatively, and equally acceptable, handle 22 may only partially circumscribe an exterior portion of shaft 12.

With continued reference to FIG. 1, it can be seen that exercise device 10 is typically an elongated, generally uniformly shaped (e.g., generally cylindrical) apparatus.

The overall length, L₁, of the elongated, generally cylindrical exercise device 10 can range from about 120 cm to about 180 cm, as well as lengths in between these two values. For example, and without limitation, suitable lengths of the exercise device 10 of the present invention include an overall length L₁ of about 122 cm, about 152 cm, or about 172 cm. In accordance with one aspect of the present disclosure, and as illustrated in FIG. 1, first and second counterweights 18 and 20 may be of the same general shape as shaft 12; that is, both the shaft 12 and the counterweights 18 and 20 may be substantially cylindrical in shape, and/or have a similar cross-sectional shape. Optionally, and equally acceptable, the shaft and the counterweights may be of a different shape, as will be described in more detail below.

The external diameters of the counterweights, d₁, and the diameter of the shaft 12, d₂, is generally such that d₁>d₂. For example, in accordance with one aspect of the present invention, the diameter d₁ of the counterweights 18 and 20 may be in the range from about 2 cm (¾ inch) to about 25.4 cm (10 inches), including diameters of about 1 cm, about 1.3 cm, about 1.9 cm, about 2.5 cm, about 3.2 cm, about 3.8 cm, about 4.0 cm, about 5.0 cm, about 6.35 cm, about 7.6 cm, about 8.9 cm, about 10.2 cm, about 11.4 cm, about 12.7 cm, about 15.2 cm, about 17.8 cm, about 20.3 cm, about 22.9 cm, about 25.4 cm, and about 26 cm, as well as values between any two of these ranges, i.e. from about 3.3 cm to about 11.5 cm, or about 5.1 cm. The diameter d₂ of the shaft 12 of device 10 is preferably in the range from about 1 cm (about ⅜ inches) to about 8 cm (about 3.1 inches), more preferably from about 1 cm (⅜ inches) to about 2.5 cm (1 inch) in diameter, and more preferably from about 1 cm (⅜ inches) to about 1.9 cm (¾ inches). In accordance with an aspect of the present invention, the ratio of the diameter d₁ of the counterweights to the diameter d₂ of the shaft is about 2:1, as exemplified by a device having a counterweight diameter, d₁, of about 1.5 inches and a shaft diameter d₂ of about 0.75 inches.

The shaft 12, as well as solid counterweights 18 and 20, in accordance with aspects of the present invention, may be made from the same or different materials, including but not limited to fiberglass, metals, polymeric materials, and combinations thereof In accordance with certain aspects of the present invention, the exercise apparatus, including both the shaft 12 and couterweights 18 and 20, are preferably comprised of polymeric materials, which may be the same or different. Preferred types of polymeric materials include, but are not limited to, nylon, acetal homopolymers and co-polymers, ultra high molecular weight polyethylene and polypropylene, acrylic polymer, polyetherimide, polyether-ketone type polymers, especially a multi-ether polymer, acrylonitrile, butadiene-styrene type polymers, polyesters, polyester-vinyl polymers, polybutylene-terephthalate type polymers, polyaramid homo and copolymers and mixtures thereof, polyphenylene sulfide homo and copolymers, halogenated vinyl type polymers, polyamide-imide type polymers, polyvinylidene flouride type polymers, polyurethane polymers, phenolic type polymers, polypropylene and polypropylene-type polymers, and combinations thereof Preferably, the exercise apparatus of the present invention are comprised of acetal homopolymers, acetal co-polymers, polyurethane type polymers, and polypropylene type polymers. More preferably, the exercise apparatus of the present invention is made from an acetal co-polymer or an acetal homopolymer.

Also suitable for use in combination with the polymeric materials listed above are optional fibers which can be used as fillers so as to increase the flexure strength of the polymeric material as desired. Such optional fibers suitable for use with the apparatus of the present invention include, but are not limited to, glass fibers, carbon fibers, nylon fibers, polyesters, cellulose, steel wool and steel fibers (e.g., steel yarn), aramid fibers, imide fibers, and combinations thereof Particulate fillers may also be used to modify properties of the polymeric material used in manufacturing the exercise apparatus described herein. Particulate fillers suitable for use herein include but are not limited to carbon, talc, cellulose, titanium dioxide, silica, metallic powders and combinations thereof The fibers used as fillers may be generally from about 0.10 to about 1.0 inches long. The length will depend upon the mixing facilities used to combine the ingredients before the shaft is formed by extruding or molding the polymeric material to form the shaft. In accordance with an aspect of the invention, preferred types of fibers include but are not limited to glass fibers, nylon fibers, polyamide fibers, polyaramide fibers, and combinations of such fibers.

The handle or hand grip 22 on elongated shaft 12 is for contact with the hand of the user with the device 10, and is preferably made from a soft rubber or soft polymeric material, such as that used in making golf club handles. Other suitable materials for use include but are not limited to fabric, leather, wood (including wood-based and wood-like materials), plastic, foams, or combinations of such materials. Handle 22 may be in the form of a single, substantially cylindrical piece with a central opening therein for the passage of shaft 12, wherein the central opening substantially circumscribes at least more than have of the external circumference of shaft 12. Optionally, handle 22 may be in the form of two or more pieces which come together to form a cylindrical shape having a toroidal cross section (i.e., having a central opening), wherein the two or more pieces form a handle around and substantially circumscribe shaft 12, and are adjoined together with any number of suitable fasteners or adhesives known in the art. In another embodiment, handle 22 may have a tapered shape, either tapered in a manner such that the narrowest diameter is near the middle of the handle, or tapered such that the narrowest diameter is near the ends of the handle, and the thickest diameter is near the middle of the handle. Handle 22 may also be tightly fitted or attached to shaft 12 in any number of ways known to those of skill in the art, such as by the use of a suitable adhesive or cement. In one embodiment, handle 22 may be fitted to shaft 12 so as to be slidably engaged to shaft 12, allowing it to be moved laterally along the length of shaft 12 (parallel to central axis 15) as desired by the user, so as to adjust weight distribution. Preferably, however, in the course of normal use of the exercise apparatus of the present invention, at least a portion of the handle covers a portion of the middle section of the shaft 12 of the exercise device.

Returning to the figures, the details of how an exercise device 10 in accordance with the present disclosure can be assembled is illustrated in FIG. 2. Typically, shaft 12 and counterweights 18 and 20 are formed separately, by any number of known processes, including but not limited to extruding, molding, mold-forming, casting, form-filling, machining, shaping, and the like. Counterweights 18 and 20 may be made with a central cavity 24, extending a distance d₃ into one end of the counterweight. Cavity 24 preferably is of substantially the same diameter as shaft 12, and distance d₃ is preferably from about ¼ to about ⅓ of the total overall length of the counterweight. During manufacture, counterweights 18 and 20 can be heated to a temperature such that width w₁ of cavity 24 expands slightly to a new width w₂ (not shown), wherein w₂>w₁, allowing an end of shaft 12 to be inserted distance d₃ into the counterweight. The apparatus is then allowed to cool, during which time cavity 24 contracts to its original width w₁ and in so doing forms a tight seal against shaft 12. Similarly, the shaft can be cooled instead of, or in addition to, heating the counterweights to cause a change in relative dimensions due to relative temperature differences. Optionally, and in accordance with the present invention, central cavity 24 can have threadable grooves (not illustrated) machined into the side walls of the cavity, and the distal and proximal ends of shaft 12 can have threads machined onto the exterior surface, such that shaft 12 can be threadably inserted into central cavity 24 an appropriate distance d₃. As a further optional aspect in accordance with the manufacture of plyometric exercise devices 10 as described herein, an optional adhesive composition can be used to further strengthen the attachment of shaft 12 to central cavity 24 of the counterweights. As known to those of skill in the art, the choice and use and choice of such adhesives will depend upon the material that shaft 12 and counterweights 18 and 20 of device 10 are made of.

The cross section of the plyometric exercise device 10 of the present invention can be any number of shapes, as illustrated in FIGS. 3A-3D. Specifically, the cross-section of both the shaft and/or the counterweights in association with the present invention can be circular, oval, or polygonal in shape in cross section, including but not limited to hexagonal (FIG. 3B), octagonal (FIG. 3C), and dodecahedral (FIG. 3D). In general, the cross-section of the elongated shaft 12 and/or the counterweights 18 and 20 can be varied in such a way so that, as explained in more detail below, the apparatus oscillates in a biased omni-directional manner and not in a perfect linear motion.

The general use of the plyometric exercise apparatus of the present invention will now be described. While only a limited number of exercises are shown, those of skill in the art will know that a plurality of exercises and movements can be performed with the apparatus described herein, in order to obtain a full range of exercise of the shoulder musculature. As used herein, shoulder musculature refers not only to the muscles comprising the shoulder itself, but also to those muscles, tendons, and ligaments in the upper arms and shoulders which are typically associated with the shoulder and its normal use. In typical operation, as illustrated in FIGS. 4 and 5, a user 50 grasps plyometric exercise apparatus 10 by handle 22 which is preferably at about the middle of apparatus 10. The user then begins to move their arm 30 in a back and forth motion (32), while simultaneously slowly and incrementally moving the apparatus 10 in an outward direction from their body, as represented by the arrow. As the user moves their arm in back and forth motion 32, plyometric apparatus 10 oscillates, for example, at a rate of from about 1 to about 2.7 cycles per second. As apparatus 10 oscillates, the counterweights on the opposite ends of the shaft of apparatus 10 oscillate, but due to the geometrical cross-section of apparatus 10, oscillate in a biased omni-directional manner. This omni-directional movement of apparatus 10 is illustrated generally by arrows 34 a and 34 b in FIG. 4. Depending upon the cross-sectional shape of plyometric apparatus 10, the omni-directional movement of the apparatus during use will approach, but not equal or become equivalent to, a movement that is coplanar with the back and forth motion 32 by the user.

FIG. 5 illustrates another embodiment of a different shoulder exercise using the plyometric exercise apparatus of the present invention. A user 50 begins with apparatus 10 grasped palm down against their waist. The user then begins to move their arm 40 in an up-and-down manner (illustrated by the arrows), while slowly raising apparatus 10 upward to a point at or substantially parallel to the users shoulder height. As apparatus 10 transfers the up-and-down arm movement of the user to energy, it begins to oscillate at a frequency from about 1 to about 2.7 cycles per second, while at the same time oscillating in an omni-directional manner as represented by arrows 42 a and 42 b. As also shown in FIG. 5, as the oscillation frequency approaches 2.5 to 2.7, and the omni-directional movement approaches, but does not become, co-planar with the up-and-down movement of the user's arm, shaft 12 can begin to exhibit a “flexing” which further contributes to the omni-directional movement of apparatus 10.

As mentioned above, and in accordance with aspects of the present invention, during normal use, the apparatus described herein preferably oscillates in the range from about 1 to about 2.7 cycles per second. For example, the apparatus as described herein can oscillate at about 1.1 cycles per second, about 1.2 cycles per second, about 1.3 cycles per second, about 1.4 cycles per second, about 1.5 cycles per second, about 1.6 cycles per second, about 1.7 cycles per second, about 1.8 cycles per second, about 1.9 cycles per second, about 2.0 cycles per second, about 2.1 cycles per second, about 2.2 cycles per second, about 2.3 cycles per second, about 2.4 cycles per second, about 2.5 cycles per second, about 2.6 cycles per second, and about 2.7 cycles per second, as well as ranges in between any two of these values, i.e. from about 2.0 to about 2.5 cycles per second.

The plyometric exercise apparatus of the present invention can be used to develop the shoulder and upper arm strength of athletes participating in a number of sports where such muscle co-ordination and strength development is important not only for performance, but to minimize the occurrence of muscle injury. Such sports include baseball, especially pitchers; volleyball; tennis; badminton; lacrosse; football; javelin throwers; jai-alai; and rock climbers/mountaineers. The plyometric exercise apparatus of the present invention can also be useful as a sports injury/wellness device, in that it could provide for muscle recovery exercises following injury. Additionally, it is envisioned that the apparatus of the present invention could also be used to develop the strength of other muscles, tendons, and ligaments in the arms and upper torso (i.e., the back) of a user.

While compositions and methods have been described in terms of “comprising” various components or steps (interpreted as meaning “including, but not limited to”), the compositions and methods can also “consist essentially of” or “consist of” the various components and steps, such terminology should be interpreted as defining essentially closed-member groups.

All of the apparatus and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the methods and apparatus of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the methods and/or apparatus and in the steps or in the sequence of steps of the methods described herein without departing from the concept and scope of the invention. Additionally, it will be apparent that certain agents which are chemically or materially related may be substituted for the agents described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the scope and concept of the invention. The present invention has been described in the context of preferred and other embodiments and not every embodiment of the invention has been described. Obvious modifications and alterations to the described embodiments are available to those of ordinary skill in the art. The disclosed and undisclosed embodiments are not intended to limit or restrict the scope or applicability of the invention conceived of by the Applicants, but rather, in conformity with the patent laws, Applicant intends to protect all such modifications and improvements to the full extent that such falls within the scope or range of equivalent of the following claims. 

1. A plyometric exercise apparatus, comprising: a longitudinally extending shaft having a proximal end, a distal end, and an external diameter d₂; a handle attached to the shaft intermediate between the proximal end and the distal end; and a first counterweight and a second counterweight, having a diameter d₁, wherein the first counterweight is attached to the proximal end of the shaft and the second counterweight is attached to the distal end of the shaft, and wherein during operation the device has a biased omni-directional movement.
 2. The exercise apparatus of claim 1, wherein at least one of the shaft, the first counterweight, or the second counterweight are comprise of nylon, acetal homopolymers and co-polymers, ultra high molecular weight polyethylene and polypropylene, acrylic polymer, polyetherimide, polyether-ketone type polymers, especially a multi-ether polymer, acrylonitrile, butadiene-styrene type polymers, polyesters, polyester-vinyl polymers, polybutylene-terephthalate type polymers, polyaramid homo and copolymers and mixtures thereof, polyphenylene sulfide homo and copolymers, halogenated vinyl type polymers, polyamide-imide type polymers, polyvinylidene flouride type polymers, polyurethane polymers, phenolic type polymers, polypropylene and polypropylene-type polymers, and combinations thereof
 3. The exercise apparatus of claim 1, wherein the shaft, the first counterweight and the second counterweight are comprised of a polymeric material selected from the group consisting of acetal co-polymers, acetal homo-polymers, nylon, polypropylene, and mixtures thereof
 4. The exercise apparatus of claim 1, wherein the diameter d₁ is greater than the diameter d₂.
 5. The exercise apparatus of claim 1, wherein the ratio of counterweight diameter d₁ to shaft diameter d₂ is about 2:1.
 6. The exercise apparatus of claim 1, wherein the apparatus has an overall length from about 120 cm to about 180 cm.
 7. The exercise apparatus of claim 1, wherein the first counterweight and the second counterweight are attached to the proximal and distal ends of the elongated shaft in a manner such that the apparatus is generally an elongated cylindrical shaft that is symmetrical about the longitudinal axis.
 8. The exercise apparatus of claim 1, wherein the shaft, the first counterweight and the second counterweight have a substantially circular cross section.
 9. The exercise apparatus of claim 1, wherein a rate of oscillation is from about 1 to about 2.7 oscillations per second.
 10. A method of exercising using a plyometric exercise apparatus that oscillates in an omni-directional manner during use, the method comprising: providing a plyometric exercise apparatus having an elongated shaft with counterweights at opposing ends and a substantially circular cross section; grasping the plyometric exercise apparatus near the middle of the elongated shaft; and moving the plyometric exercise apparatus back and forth so as to cause the counterweights at the opposing ends to oscillate in a biased omni-directional manner, wherein the back and forth movement and the omni-directional oscillation are not coplanar.
 11. The method of exercising of claim 10, wherein the grasping step includes grasping a handle portion located at the middle portion of the elongated shaft.
 12. The method of exercising of claim 10, wherein moving the plyometric exercise apparatus occurs at a rate of about 1 to about 2.7 oscillations per second. 